(1) Field of the Invention
This invention generally relates to an apparatus for controlling pressure recovery. More particularly, the invention relates to an apparatus for controlling pressure recovery in a submarine cylindrical shutter way/guide-can recess.
(2) Description of the Prior Art
The current art and known construction of a submarine torpedo launchway causes a substantial recovery of dynamic pressure in a cylindrical shutterway/guide-can recess (SGR).
Referring to the conventional art of FIG. 1, the known SGR is illustrated therein. Specifically, the portion of the submarine showing the launchway location of a torpedo T prior to launch is depicted in general by reference number 10. The launchway 10 includes a shutterway 12, and a guide-can recess 14 in longitudinal alignment with the shutterway 12. An entering flow of sea water 16 passes into a first end 12a of the shutterway 12 and enters the guide-can 14 at a passage opening 18 at a second end 12b of the shutterway 12 and a first end 14a of the guide-can 14. The guide-can 14 and shutterway 12 are those portion of the launchway 10 through which the torpedo T passes upon firing the torpedo from the submarine.
The second end 14b of the guide-can 14 terminates in an opening, thereby defining an open area 20 between the guide-can 14 and a launch tube 22 of the submarine. The entering flow 16 becomes either stagnation flow 24 or redirected flow 26 as explained in the following.
Just prior to launch, when a muzzle door (not shown) of the torpedo launch tube 22 has opened, the pressure head of water that has built up at the entrance to the launch tube 22, or otherwise termed xe2x80x9crecovered pressurexe2x80x9d, induces an adverse pressure gradient along a length of the torpedo T while the torpedo is in the tube 22. An adverse pressure gradient means that the pressure is higher at the nose of the torpedo compared to the pressure at its tail end. This condition energizes a breechward movement of the torpedo T that could result in structural damage to the weapon if this condition becomes excessive. Furthermore, fluid flow from the torpedo tube 22 to the turbine pump is reversed, thereby causing an undue stress on the turbine pump of the torpedo at start-up. Over time, this undue stress may structurally fatigue a turbine pump clutch of the torpedo.
An inspection of the submarine launchway reveals the probable cause for the adverse pressure gradient along the torpedo while in the tube 22. Specifically, the large separation between the second end 14b of the guide-can 14 and the torpedo tube 22 permits flow through the SGR and into a free-flood region 28 of the submarine. This separation is necessary to allow opening of the torpedo tube muzzle door just prior to launch of the torpedo. Note that the free flood region 28 of the submarine is formed to be outwardly concentrical with the shutterway 12/guide-can 14 portion, and receives the redirected flow 26 from the guide-can 14. It is also revealed that the free-flood region 28 is not isolated from the flow dynamics external to the hull of the shutterway 12 and guide-can 14. In particular, the sides and rear of doors to the shutterway 12 do not seat tightly against the external hull in their closed position. Large gaps which frame the shutter doors permit low-velocity flow, indicted at 28a, through the free-flood region that eventually leads to the flow dynamics external to the submarine hull. The high-momentum/low-volume flow through the SGR is supported by a low-momentum/high-volume flow through the free-flood region. The high-momentum flow through the SGR stagnates locally at the torpedo tube muzzle door as shown by 24, thereby recovering the full dynamic pressure of the flow through the SGR.
The ensuing event of the above flow path centers on flow stagnation 24 at the torpedo nose just prior to launch. Complete conversion of the dynamic pressure to static pressure gives a much higher static pressure at the torpedo nose compared to the pressure at its tail. A simple, but synonymous example, is a jet flow impinging on a flat plate where the recovered pressure is directly attributed to a quick termination of stream wise flow momentum due to the presence of the solid wall at the entrance to the torpedo tube 22. At the wall, the flow stagnates (24) and recovers its entire dynamic head. In this example, the flow redirects at 26 laterally along solid end walls 30 of the launch tube 22. Translated into submarine geometry, the flow redirects to the free-flood region 28.
Possible corrections for reducing the stagnation pressure 24 at the muzzle door/end walls 30 center on preventing any external flow from entering the SGR. Geometric modifications to the launchway include sealing the gaps between the shutter doors and the submarine hull, or enclosing the open zone 20 between the guide-can 14 and the torpedo tube 22. Although these changes address the symptoms of the recovered pressure problem, their functionality may not be one hundred percent assured. In particular, other access ports from the free-flood region 28 to the hull also generate external flow dynamics, but more importantly, fluid entrainment or its associated mass exchange entering the SGR can not be fully prevented due to the large characteristic length of the shutterway 12. These geometric fixes simply translate the recovered dynamic pressure zone to within the SGR itself. The stagnation pressure 24 at the torpedo nose may remain unchanged.
Thus, a problem exists in the art whereby there is a need to reduce or eliminate the stagnation flow or pressure head build up at the door of the launch tube 22. This should be done in a retrofit manner to accommodate existing submarine launch apparatus without undue expense or modification of the existing structure.
The following patents, for example, disclose various types of pressure recovery devices, but do not disclose an apparatus for controlling pressure recovery utilizing a plurality of retrofit circumferential chokes as occurs in the present invention.
U.S. Pat. No. 4,383,552 to Baker;
U.S. Pat. No. 5,020,943 to Filipelli; and
U.S. Pat. No. 5,521,340 to Thawani et al.
Specifically, the patent to Baker discloses an adjustable choke for automatically regulating high velocity flow through a pipe line. The choke comprises a generally cylindrical elongated body including an axially-directed inlet port at one end, means for selectively controlling flow though the regulator at the other end, and a radially-directed outlet port intermediate of the body. A pair of slidable, annular rings contained in the body adjacent the inlet port comprise an upstream ring and a downstream ring. Each of the rings are spring biased from the other. The upstream ring includes a flow passageway and a flow obstructing portion. The downstream ring includes a plurality of flow passageways, at least one of the downstream ring flow passageways being disposed out of communicable flow alignment with the upstream ring flow passageway. Upon impingement of sufficient flow against the obstructing portion of the upstream ring, the upstream ring is slid into abutment with the downstream ring for closing the one downstream ring flow passageway and for limiting fluid flow through the choke. Upon dissipation of the sufficient flow, the upstream ring is spring biased away from the downstream ring. The means for selectively controlling the flow is selectively, operatively engaged to the downstream ring whereby the downstream ring may be selectively slid into abutment with the upstream ring for closing the one downstream ring flow passageway. The means for selectively controlling also includes a selectively advanceable valve stem for closing the downstream ring flow passageways other than the one downstream ring flow passageway. It should be noted that the primary function of Baker s invention is limiting high velocity, which only indirectly limits high pressure. The proposed invention does not limit the centerline velocity, only the centerline pressure. Further, only two ring devices of complex geometry obstruct the flow in Baker s invention, rather than a series of chokes as in the proposed invention. Flow control (in Baker s invention) is obtained through structural obstruction, rather than turbulence ingestion in the main flow direction as in the proposed device. Next, the rings of Bakers""s invention do not maintain geometric similarity of the main housing geometry. Each ring contains one large diameter center hole with five surrounding small diameter holes. The proposed invention preserves geometric similarity of the main external housing. Still further, the primary flow is redirected 90 degrees from inlet to outlet in Baker s invention, whereas the flow in the proposed invention is continuous. Bakers invention requires user control to make the invention effective, whereas the proposed invention has fixed chokes.
The patent to Filipelli discloses a cylindrical pipe of internal diameter d, intended for pneumatic transport of solid polymer particles. The pipe has constrictions located over its length in such a way that the distance 1 between two consecutive constrictions is between d and 10xc3x97d. Each constriction consists of a non-uniform restriction of the cross-sectional area S of the pipe. That restriction defines a new internal cross-sectional area Sxe2x80x2 of between 0.900xc3x97S and 0.995xc3x97S and has at least one unrestricted free passage defined by a circular sector of the area S with a vertex situated on the axis of the pipe and an angle at the vertex ranging from 5 to 60. It should be noted that the Filipelli invention is not for flow control. Instead, Filipelli inserts a series of smooth rings, which are very far apart, that inhibit the formation of polymer threads. The presence of these threads would disturb and restrict the efficient transport of the polymer particles by a hot carrier gas. In addition, Filipelli does not attempt to control either the velocity or the pressure of the main flow gas.
Thawani et al. disclose an apparatus for attenuating noise produced by fluid pressure pulsations in a hydraulic system in an automotive vehicle. The apparatus includes a muffler device comprising a generally elongate tubular member having a predetermined number of attenuating zones therein, each zone having a cross-sectional area of different size than the cross-sectional area of the tubular member. The attenuating zones are spaced at unequal lengths from one another to achieve maximized noise reduction benefits. Once again, the Thawani et al. invention is not for flow control. Instead, Thawani et al. insert a series of smooth rings for the primary purpose of reducing noise in the various piping systems of an automobile. The device is actually a muffler that contains a series of smooth rings much like the Filipelli invention. These rings attenuate any pressure fluctuations that are responsible for noise. Further, Thawani et al. do not attempt to reduce either the streamwise velocity or the static pressure of the main flow.
It should be understood that the present invention would in fact enhance the functionality of the above patents by providing a plurality of retrofit circumferential chokes within the guide-can portion of a torpedo launch apparatus.
Therefore it is an object of this invention to provide an apparatus for controlling pressure recovery.
Another object of this invention is to provide an apparatus for controlling pressure recovery whereby recovered pressure is reduced within a submarine launch tube.
Still another object of this invention is to provide an apparatus for controlling pressure recovery, the apparatus containing a series of equidistant circumferential chokes for generating high turbulent activity within the submarine launch tube.
A still further object of the invention is to provide an apparatus for controlling pressure recovery where the reduction of recovered pressure is directly proportional to the number of chokes of the apparatus.
Yet another object of this invention is to provide an apparatus for controlling pressure recovery within a submarine launch tube which is simple to manufacture and easy to use.
In accordance with one aspect of this invention, there is provided an apparatus for controlling fluid pressure recovery which includes an elongated housing having an opening at a first end thereof, an opening at a second end thereof, an inner peripheral surface, and a fluid flow passageway therethrough. The apparatus further includes a plurality of choke members fixed to the inner peripheral surface of the housing, each of the plurality of choke members being spaced from an adjacent choke member and projecting a predetermined distance into the fluid flow passageway of the longitudinal housing. The plurality of choke members sequentially produce a reduced turbulent free shear fluid layer from the first end to the second end of the elongated housing.